*{
    padding: 0;
    margin: 0;
}
.box{
    width: 600px;
    height: 400px;
    border: 5px solid springgreen;
    margin: 0 auto;
}
.box ul{
    display: flex;
    list-style: none;
}
.box ul li{
    width: 200px;
    height: 50px;
    text-align: center;
    line-height: 50px;
    font-size: 30px;
    background: blue;
    cursor: pointer;
    user-select: none;
}
.box ul li.active{
    background: gold;
}
.box ol{
    position: relative;
    list-style: none;
}
.box ol li{
    display:none;
    width: 600px;
    height: 350px;
    text-align: center;
    line-height: 350px;
    font-size: 30px; 
    position: absolute;
    user-select: none;
}
.box ol li.active{
    background: deeppink;
    display: block;
}
.tab2{
    margin-top: 30px;
}